1. Field of the Invention
The present invention relates to a cleaning system and a cleaning method, and in particular, to a cleaning system and a cleaning method utilizing an oxidizing substance that is generated by the electrolysis of sulfuric acid.
2. Background Art
Such a system has been known conventionally that uses persulfate ions generated by the electrolysis of an aqueous solution of sulfuric acid to clean and remove resist etc. that has adhered to a silicon wafer etc., while circulating a persulfate solution through an electrolytic reaction vessel and a cleaning vessel (JP-A-2006-111943).
In JP-A-2006-111943, concentrated sulfuric acid of 98% is diluted with ultrapure water, which is then supplied to an electrolytic reaction vessel. Such an oxidation-activating species, for example, as peroxomonosulfuric acid that is generated through the electrolysis reaction of sulfuric acid is decomposed through reaction with water. Therefore, in order to generate stably the peroxomonosulfuric acid to enhance the efficiency of cleaning and peeling the resist etc., it is desirable to avoid carrying out an electrolysis in such a water-rich state as described in JP-A-2006-111943 wherein concentrated sulfuric acid is diluted with ultrapure water.